Winding core



June 3, 1969 w, FRASER 3,447,674

WINDING CORE Filed July 14, 1967 United States Patent 3,447,674 WINDINGCORE William T. Fraser, 24 Dartmouth Road, Mountain Lakes, NJ. 07046Filed July 14, 1967, Ser. No. 653,434 Int. Cl. B65h 75/00; B65 75/02;B65d 85/04 U.S. Cl. 206-59 11 Claims ABSTRACT OF THE DISCLOSURE A corefor rolled sheet material which is an extrusion in the form of a pair ofconcentric continuously extruded cylinders joined by continuouslongitudinal ribs.

This invention relates to winding cores of rigid plastic constructionadapted for use in the manufacture of paper, plastic films, textiles orother flexible materials generally manufactured in web form.

It is the practice in the paper and film manufacturing process, and inthe subsequent processes of their treatment or printing thereon, to Windthese webs 0n cores having a width which is governed by the width of webbeing processed.

It is also the practice in the above processes to wind rolls of paper orfilm into rolls of the largest possible diameter and width. Both thediameter and width of these rolls are very often limited by limitationsof diameter and strength of the winding core.

In practice, a core is usually of tubular shape, generally manufacturedof paper composition or of steel, and is mounted in a winding orunwinding machine by means of core chucks or mandrels. Typically, paperor steel cores are used in widths usually not less than 3 feet nor morethan 20 feet.

One of the problems with paper cores is that during the Winding orunwinding of a web under tension, the core chucks will tear up the endsor the inside surfaces of the cores. These cores therefore cannot bere-used and must be discarded. The life of a paper core is usually onewinding and unwinding process. It is then discarded as scrap.

Another problem with paper cores is that large diameter rolls of web areusually Wound on large diameter cores. These large cores must make useof steel endplates or inserts in order to be used on machines designedwith small diameter core chucks.

One of the problems with steel cores, which generally are not used forcores of less than 5 inches internal diameter, is their heavy weight.These cores require hoists or cranes to lift and position them in amachine. This operation must be done very carefully to prevent damagingthe machine or the surface of the core. A burr created on the surface ofa steel core by accidental impact will damage the bottom layers of aroll of paper or plastic film Another problem with steel cores is thehigh cost of transportation of heavy steel tubing which is used forcores, and which adds to the cost of the paper or plastic film.

Five-inch internal diameter steel cores, or larger, are so heavy andawkward to handle that their surfaces and ends are easily damaged,particularly when they are kept for re-use. The life of a steel core isgenerally not more than three winding and unwinding processes beforerequiring refinishing.

Another disadvantage of both paper and steel cores is the limitation ofthe machinery in the smaller converting plants. Many of these smallerconverters would prefer to use large diameter cores but their machinesare built with 3-inch diameter core chucks and are therefore restrictedto 3-inch diameter cores. The cost of converting the machinery isusually too high.

It has now been discovered that it is possible to prepare cores forrolled sheet material which cores are sufiiciently light in weight topermit manual handling in all sizes presently in common use. These coresare characterized by a substantial void space, and are prepared from amaterial with a specific gravity substantially less than that of steel.In addition, the instant cores are readily prepared by continuousextrusion whereby they are characterized by close tolerances and regularshape and size, which lead to freedom from eccentricity and excellentstatic and dynamic balance characteristics. The instant cores are easilycut to shorter lengths if the ends become damaged by the mandrels onwhich they are mounted during use.

A major advantage of the cores of this invention over the corespresently in use in process industries that wind webs of wide widths,generally Wider than 3 feet, is that the instant cores are so light inweight that a machine fitted with small diameter core chucks canaccommodate them even though their external diameter may be double thatof their internal diameter.

Other major advantages of this invention are that one overage man canlift a 10-inch x 15-inch core x 8 feet wide and place it in position ina winding machine without necessitating the use of a hoist, thataccidental impact between the core and a machine will not dam-age eitherthe core or the machine, that the high tensile and flexural strength ofthe plastic material, combined with its high impact resistance, allowsthe cores tobe mishandled without damage to the structure or its outersurface, thus providing a long reuseable lift, and that when a core doesbecome damaged beyond repair or use, the core may, by virtue of itsthermoplastic nature, be granulated in relatively inexpensive,commercially available granulators. The small bulk, light weight plasticmay be re-shipped back to the core manufacturer for re-processing intonew cores. This advantage offers a cost reduction to industries that usecores.

In accordance with the present invention, a rigid core for rolled sheetmaterial comprises an outer cylindrical shell and an inner cylindricalshell disposed concentrically Within said outer shell by a plurality ofuniformly circumferentially spaced axially continuous longitudinal ribs,said outer shell, inner shell and ribs being an integral unitaryextrusion of an organic thermoplastic polymeric resin. The inventionalso contemplates a package of film material wound on such a core, andthe process by which the core is made.

The invention will be further described in conjunction with theaccompanying drawings which are to be considered as exemplary of apreferred embodiment of the invention and which do not constitute alimitation thereof.

In the drawings:

FIG. 1 is a view in perspective of an extruded plastic core inaccordance with the instant invention;

FIG. 2 is a view in cross-section taken anywhere along the length ofFIG. 1; and

FIG. 3 is a view in perspective of a core in accordance with the presentinvention carrying sheet material wound thereon.

The plastic core of FIGS. 1 and 2 is of a length at least ten times itsdiameter. It comprises an outer cylindrical shell 10 within which isdisposed an inner cylindrical shell 12. The shells are concentricallyarranged and are spaced and held in position by four ribs 15. Theconcentric cylindrical shells and the ribs are extruded as an integralunitary structure through a die from rigid, unplasticized polyvinylchloride resin.

The outer peripheral surface of the outer cylinder is completely smoothand is devoid of any projection or burrs of any kind. However, thissurface may contain depressions or recesses therein such as an adaxialreentrant groove 20 which extends axially lengthwise of the core for theentire length thereof. As illustrated, this groove is preferably ofdovetail shape, thus providing a recess for the insertion of the end offilm material which is to be wound on the core (so as to assist the filmin grasping the core without slipping therefrom under the tensionnormally applied to film when it is wound on such cores). Thedisposition of the groove 20 in a plane with two of the ribs facilitatesappropriate design of the shape of the extrusion plate through which thepolyvinyl chloride resin is extruded to form the instant core such thatthe resin is so disposed throughout the cross-section of the core thatthe core is balanced both statically and dynamically about itslongitudinal axis.

The core of FIGS. 1 and 2 contains approximately 50 percent void space,a void space of from about to 70 percent being preferred for the instantcores. The polyvinyl chloride resin used in the core of FIGS. 1 and 2has a specific gravity of about 1.3. This polyvinyl chloride isunplasticized, and is characterized by an average molecular weight onthe order of about 60,000, a tensile strength at room temperature of7,500 pounds per square inch, a flexural strength of about 12,000p.s.i., and a compressive strength of about 9,000 p.s.i.

FIG. 3 illustrates a core 50 having an external diameter approximatelytwice its internal diameter, on which a continuous plastic film 52 iswound to form a final package having a diameter of at least about sixtimes the outer diameter of the core 50.

The material preferred for use in the construction of this core is ahigh molecular weight vinyl chloride polymer of the suspension type. Thenumber average molecular weights are on the order of 60,000, but mayrange from 10,000 to considerably more than 100,000.

The basic polyvinyl chloride resin, compounded with heat stabilizers,fillers, modifiers, lubricants and pigments, and extruded into the shapeof this invention, results in a noncorrosive core of light weight, highstrength, high impact resistance, and great rigidity.

Although polyvinyl chloride is the preferred polymer material forfabrication of the instant cores, other polymeric resins may be usedprovided they are characterized by a tensile strength at roomtemperature (i.e. 70 F.) of at least about 4,000 pounds per square inch,and a specific gravity at roomtemperature less than about 2.

An example of another suitable type of resin is the polycarbonate class.

The instant cores suitably may be prepared by fusing suitable resin andexpressing it through a die such as to give the desired instantstructure. These extrusion techniques are, in general, well known in theart. The continuous core so produced may be cut into lengths appropriatefor use, which normally will be on the order of at least ten diameters,and, as referred to hereinabove, characteristically are highly rigid,maintain critical tolerances of dimension, concentricity, balance,surface smoothness and freedom from projections. They typically are oftotally plastic, unitary integral construction, of continuously uniformtransverse cross-section throughout their length, readily reclaimed andreprocessed by fusion and re-extrusion, and, by virtue of theirsignificant void space and fabrication from a material of low specificgravity, suitable for manual handling in sizes presently requiring theuse of hoists and other machinery.

It is to be understood that the Abstract given above is for theconvenience of technical searchers and is not to be used forinterpreting the scope of the invention, and various changes may be madein details of construction without departing from the true spirit of theinvention. Thus, for example, although a rigid core having four ribs hasbeen illustrated, it is quite possible to utilize three, six, eight orany other desired number of ribs within the scope of the invention.

What is claimed is:

1. A rigid core for rolled sheet material comprising an outercylindrical shell, and an inner cylindrical shell disposedconcentrically within said outer shell by a plurality of uniformlycircumferentially spaced axially continuous longitudinal ribs, saidouter shell, inner shell and ribs being an integral unitary extrusion ofan organic thermoplastic polymeric resin and said core having a lengthaxially at least ten times its maximum diameter.

2. A rigid core for rolled sheet material as set forth in claim 1 inwhich said organic thermoplastic polymeric resin has a tensile strengthof at least about 4,000 pounds per square inch.

3. A rigid core for rolled sheet material as set forth in claim 1 inwhich said ribs, the inner surface of said outer shell, and the outersurface of said inner shell define a void space, said void spaceconstituting at least about 20 percent of the cross-sectional areabetween the outer surface of said outer shell and the inner surface ofsaid inner shell.

4. A rigid core for rolled sheet material as set forth in claim 1 inwhich said organic thermoplastic polymeric material has a specificgravity of less than about 2.

5. A rigid core for rolled sheet material as set forth in claim 1 inwhich the outer surface of said outer cylindrical shell carries anadaxial re-entrant groove which extends continuously lengthwise of thecore.

6. A rigid core for rolled sheet material as set forth in claim 1 inwhich said outer peripheral surface is smooth and free of anyprojections or burrs.

'7. A rigid core for rolled sheet material as set forth in claim 1 inwhich said thermoplastic polymeric resin is unplasticized polyvinylchloride.

8. A rigid core for rolled sheet material as set forth in claim 1 inwhich there are four of said ribs.

9. A rigid core for rolled sheet material as set forth in claim 1 inwhich said axial length is at least three feet.

10. A rigid core for rolled sheet material as set forth in claim 5 inwhich said groove is located in a plane with two of said ribs and saidresin is so disposed throughout the cross-section of said core that saidcore is balanced both statically and dynamically about its longitudinalaxis.

11. A package of sheet material which comprises an inner cylindricalshell disposed concentrically within an outer cylindrical shell by aplurality of circumferentially spaced axially continuous longitudinalribs, said inner shell, outer shell and ribs being an integral unitaryextrusion of an organic thermoplastic polymeric resin and said corehaving a length axially at least ten times its maximum transversediameter, and a Web of sheet material rolled about said outercylindrical shell, the width of the web substantially corresponding tosaid axial length of the core and said package having a diameter of atleast about six times the outer diameter of said core.

References Cited UNITED STATES PATENTS 2,659,543 11/1953 Guyer 242-6852,693,918 11/1954 Bretson et al 242-685 2,551,710 5/ 1951 Slaughter.

JAMES B. MARBERT, Primary Examiner.

US. Cl. X.R. 242-68.5

